We have started using the Irrometer 200SA sensor in one of our products. We are using an AVR series micro-controller and we have followed the hardware instructions provided by the Irrometer team. We have used Multiplexer to use more than 1 sensor in a device.
Now as per our testing, we are getting a good response i.e. we can clearly see the changes when the irrigation is done ( screenshot attached ).
Now the problem i am facing is % changes in the readings while in the same environment ( we are sensing every 10 minutes ). In the same environment, the resistance which we are calculating is changing up to 9% also ( below is the reading and corresponding changes ). I have few questions
If you convert the resistance to CB ( centibar - this is what any agronomist will use ), the change in CB is negligible ( using their calibration lookup table) as per our resistance values.
Is the sensor readings suppose to change this much within 10 minutes?
Irrometer guys have not published any resolution or accuracy. This means there is no way, I can find out if the resistance values can vary this much % between corresponding readings. There is no data on repeatability published by them.
Does anyone else has used these sensors and came across these issues of % changes in the corresponding readings even in almost the same soil conditions?